EFI/Carb Why Different Gearing?

3297 Views 3 Replies 3 Participants Last post by chiselchst, Mar 11, 2002

chiselchst

Discussion Starter · Mar 10, 2002

I understand that the EFI bikes are geared a little lower than carbed bikes, so that they run at higher RPM's than a carbed bike for an equal speed. Is this true, and why is that?

If anything I would have guesed it to be the other way around...

Thanks,
Mitch

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logical

· #2 · Mar 10, 2002

It is different on the touring bikes that give you a carb/EFI choice but the same on Softails that have a choice. The touring EFI bikes have higher ratios which would mean higher RPMs for a given speed...about 7%. My guess is that the torque curves are a little different for the two and they are just tweaks. I suppose it could also have to do with the slightly higher EFI idle speed. Disclaimer: the preceeding is a wild guess.

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HIPPO

· #3 · Mar 10, 2002

I think the answer is to be found in the history of the EFI touring bikes. When they first came out with the Marelli injection and the EFI bikes cost significantly more then an otherwise equal carb bike and the EFI bikes could be considered the flagships, at least from the factories point of view, it just wouldn't do for them to be outperformed.

So, they gave the EFI bikes lower gearing and better cams. They still were outperformed but the issue was confused enough for plausible deniability at least with the general public.

Fast forward to 02, just before the Delphi touring bikes came out there was a lot of conflicting information from the factory regarding the gear ratios. They must have played with the idea to use the same ratio on both bikes.
While in totally stock form the Delphi bikes slightly outperform the carb bikes overall, even a totally stock carb bike will pull better from very low rpm. The Delphi bikes definitely hate low rpm, so they probably figured they may be better off leaving the lower gear ratio in for the EFI bikes.

It really is a strictly academic issue, there is no reason whatsoever why they shouldn't run all day long at 4000 or even 4500 rpm.

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chiselchst

Discussion Starter · #4 · Mar 11, 2002

Thanks for the replies...there is some history there I didn't know about.

I guess these models (FLH's) are expected to be asked to carry more weight on average, so lower gearing does makes sense.

After riding several miles together, I noticed I do shift a tad sooner that my partners on a Fatboy and a Heritage. Each person has his own riding style, and everyone varies on shift points (especially with "pipes"), but I was usually shifting a tad sooner than my friends on other models. Now that makes sense...

Thanks again,
Mitch

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